Joseph Miller
Analyst · H.C. Wainright
Thank you, Peter, and good morning, everyone. Let's take a few minutes and go into detail regarding our financial results for the first quarter of 2024. Total net revenue was $50.3 million and $34.4 million for the 3 months ended March 31, 2024, and March 31, 2023, respectively.
Net product revenue over the same period was $48.1 million and $34.3 million, representing growth of approximately 46% and 40%, respectively. The increase is primarily due to an increase in LUPKYNIS sales from our 2 main specialty pharmacies, driven predominantly by further penetration of the LN market.
Total cost of sales and operating expenses inclusive of onetime restructuring charge in Q1 2024 were $63.6 million for the quarter ended March 31, 2024, and $64 million for the quarter ended March 31, 2023. It is important to note that the first quarter was fairly burdened from an operating expense standpoint as the restructuring charge was not fully implemented until late in the first quarter of 2024.
Let me now give you a further breakdown of operating expenses, drivers and fluctuations. Cost of sales was $7.8 million for the quarter ended March 31, 2024, and $421,000 for the quarter ended March 31, 2023. The increase is primarily due to increased sales of LUPKYNIS, coupled with the amortization of the mono plant finance right-of-use asset, which was placed into service in late June 2023.
Gross margins for the quarter ended March 31, 2024, and March 31, 2023, was approximately 85% and 99%. Selling, general and administrative expenses, inclusive of share-based compensation were $47.7 million and $50.1 million for the 3 months ended March 31, 2024, and March 31, 2023, respectively.
The primary drivers for the decrease were lower corporate costs, employee-related costs due to the reduction in headcount, which occurred late in the first quarter of 2024 and lower spend for travel. The decrease in SG&A operating expenses reflects the early impact of our restructuring efforts though this balance does not include the onetime restructuring charge.
The onetime restructuring charge is reflected as a stand-alone line item in the profit and loss statement and will be discussed separately in a moment. Noncash SG&A share-based compensation expense was $7.5 million for the first quarter of 2024 and $7.6 million for the prior year period.
Research and development expenses, inclusive of share-based compensation expense was $5.6 million for the quarter ended March 31, 2024, and $13.2 million for the quarter ended March 31, 2023. The decrease is primarily related to exiting our pipeline programs as previously announced, but does not include the impact of the onetime restructuring charge, as previously mentioned, the onetime restructuring charge is reflected as a stand-alone line item.
Noncash share-based compensation expense included within R&D expense was a credit of $2.2 million and an expense of $1.6 million for the quarters ended March 31, 2024, and March 31, 2023. The primary driver for the decrease in share-based compensation is related to the reduction in headcount, which occurred late in the first quarter of 2024.
Restructuring expenses for the quarter amounted to $6.7 million in the prior year period to 0. The balance is primarily made up of employee severance and onetime benefit payments and contract termination costs. The company has recognized most of its planned restructuring costs in the first quarter.
Other income was $4.1 million and interest expense was $1.3 million for the quarter ended March 31, 2024, compared to other expense of $290,000 and no interest expense for the prior year period. The changes for both other income and interest expense related to our mono plant finance right-of-use asset, which is denominated in Swiss francs and was placed into service in late June 2023.
Interest income was $4.5 million for the quarter ended March 31, 2024, and $3.8 million for the prior year period. The increase is due to higher yields on our investments as a result of increased interest rates. Aurinia recorded a net loss of $10.7 million or $0.07 net loss per common share for the quarter ended March 31, 2024, as compared to a net loss of $26.2 million or $0.18 net loss per common share for the quarter ended March 31, 2023.
As of March 31, 2024, Aurinia had cash, cash equivalents and restricted cash and investments of $320.1 million compared to $350.7 million at December 31, 2023. The decrease is primarily related to continued investment in commercialization activities and post-approval commitments of our approved drug, LUPKYNIS, Monoplant payments, share repurchases and restructuring-related payments, partially offset by an increase in cash received from sales of LUPKYNIS.
The company remains debt free at March 31, 2024. With that, I would like to hand the call back over to Peter for some closing remarks. Peter?